Process of making magnetic material.



WILLIAM E. RUDER,

, as an OF SCiHENECTAIDY, NEW YORK, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

PROCESS OF MAKING MAGNETIC MATERIAL.

No Drawing.

' T 0 all whom it may concern Be it known that I, WILLIAM E. Room, acitizen of the United States, residing at Schenectady, in the county ofSchenectady, State of New York, have invented certain new and useful.Improvements in the Process of Making Magnetic Material, of which thefollowing is a specification.

' My invention has reference to the conversion of ordinary unalloyed,oxygenous iron, and especially of commercially pure unalloyed, oxygenousiron, particularly in sheet form, to a new state in which this materialexhibits improved magnetic qualities which are especially useful intransformer cores, and in cores or frames for other alternating currentapparatus. 4 i

I have heretofore discovered that the hysteresis of silicon steel isgreatly reduced by the coalescence of the normal small grains of thematerial, which the unaided eye cannot resolve, into grains that arelarge enough to appear separated to the unaided eye, and by removingfrom the material all impurities such as sulfur, phosphorus and carbon,butparticularly the oxygen which is combined w1th or is occluded in themate-' rial, so that all oxidulated compounds in the steel becomereduced and the new material becomes practically non-oxygenous. For therealization of this discovery I have invented a process, and havesecured a Patent, No. 1,110,010, dated September 8, 1914. The specificprocess described in my aforesaid patent consists in subjecting thesilicon steel to a high temperature either in a partial vacuum (undera-gas pressure at or below the dissociation pressures of the oxids .in

' the materiaLfor the prevailing temperature) particularly or in anatmosphere of a reducing gassuch as hydrogen;- and in the said patent Ih'ave described and illustrated suitable apparatus for practisingthesaid invention.

Now, the low hysteresis property imparted to silicon steel by theprocessdescribed in'my aforesaid patent can also be imparted to ordinaryunalloyed, oxygenous iron and to commercially pure iron, such as isproduced by the open hearth-or Bessemer-or crucible process, and, inaddition,

a valuable property not possessed by silicon steel can be imparted tosuch ordinary iron, namely, exceptionally high permeability. Theseresults can be obtained by performing upon such ordinary ironsubstantially the Specification of Letters Patent.

Patented Oct. 17, rare.

same acts which result in the improvement of silicon steel in accordancewith my aforesaid ipatent. I have also discovered that the property ofnon-aging, which heretofore was believed t9 be dependent upon thepresence of silicon or other alloying materials in the iron, can by thesame acts, also be imparted to unalloyed, oxygenous iron." The new;product is practically free of sulfur,

phosphorus, carbon and oxygen and it shows substantially the same largegrains as the improved silicon steel. In addition to this the-new rawmaterial used, namely, either ordinary or commercially pure unalloyed,oxygenous iron,- being far less brittleand much softer than siliconsteel, can be produced and subjected to the process in thinner sheetswhich is a considerable advantage, particularly for alternating currentapparatus, and the purifying effect of the process extends more nearlythroughout its mass than in the case of the necessarily thicker sheetsof silicon steel, so that the new product may be made more nearlynon-oxygenous than silicon steel, and, of course, much cheaper thansilicon steel.

In practising the process any suitable apparatus, especially those fullyshown and described in my aforesaid patent'may be employed and itis,therefore, unnecessary to here again show and describe the same; a

reference to the patent is deemed'sufficient. The nature of the rawmaterial, ordinary or commercially pure unalloyed, :oxygenous iron,however, prohibits the use of such high temperatures as may be andpreferably are employed in the case of silicon steel. With silicon steelI have used temperatures reachingas high as I325 C. with good effect,but with ordinary or commercially pure unalloyed, oxygenous iron I havefound that the practical upper limit is about 1200 C.,-beyond which itis not necessary to go nor is it advisable to exceed this temperature onaccount of the danger of the sticking together of the sheets, which inpractice are subjected to the process in packs.

The process is as follows: Ordinary commercial unalloyed, oxygenous ironor socalled commercially pure iron (known as American ingot ironpreferably in packs as hydrogen, is passed in a continuous stream,'for aperiod of from 2 to 8 hours, depending upon the mass of the material andthe temperature employed, the greater mass requiring a longer period andthe higher temperature permitting a shorter period. The apparatus shownin my Patent No. 1,110,010, are well adapted for this purpose, and ifthe vacuum furnace is employed, it should be maintained at a lowpressure, at

about 2 to 2.5 millimetersaof mercury," thelower pressure beingpreferable. The con- 1 verted material should be allowed tocool in thefurnace to a point where its removal and consequent exposure to the a1rw ll not cause any appreciable oxidation. 7 This process isdistinguished from that of heating electrolytic iron in vacuum, which isindicated in the current literature of the 20 art.

tains among its traces of impurities no oxygen; but it containshydrogen, which is in the nascent state (H) when it is liberated by theelectrolysis together with the iron; it

,is exceedingly active and forms with the iron an alloy which is veryhard and brittle. This alloy is broken up and the hydrogen is driven offby heating the. material in vacuum.

It is conceivable (although the fact has not yet been ascertained) thatif in the practice of my process a hydrogen gas (H atmosphere isemployed, traces of such gas become occluded in the iron; but such gas,

unlike nascent hydrogen, does not alloy with the iron and renders thematerial neither hard nor brittle; nor has it any other deleteriouseffect.- i

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. The process of making low hysteresis,"

highpermeability and non-agmg magnetic material by annealing, whichconsists in subjecting commercial unalloyed, oxygeiious iron to oxygenremoving conditions at a high temperature belowthat of fusion.

2. The process of making low hysteresis, high permeability andnon-aging'magnetic material by annealing, which consists in subjectingcommercial unalloyed, oxygenous iron to a high temperature below that offusion under a gas pressure at or below the dissociation pressures ofthe oXids in the iron for the prevailing temperature.

3. The process of making low hysteresis,

high permeability and non-aging magnetic material by annealing, whichconsists in heating commercial unalloyed, oxygenous iron to or above 760C. but below the fusing temperature in a partialvacuum.

4. The process of making low hysteresis, high permeability and non-agingmagnetic material by annealing, which consists in heating. commercialunalloyed, oxygenous iron to a temperature of 760 C. to 1200 C. under amaintained gas pressure of about 2 to 2.5 millimeters of mercury.

5. The process of making low hysteresis,

high permeability and non-aging magnetic material by annealing, whichconsists in subjecting commercial unalloyed, oxygenous iron to oxygenremoving conditions at a temperature at least as high as 760 C. butbelow the temperature of fusion.

In witness-whereof, T have hereunto set my hand this 5th day of April,1916.

' WILLIAM E. RUDER.

